In this study, we investigated the functions that reproduce the configurational heat capacity (Cconfig) that occurs above the glass transition temperature for polystyrene (PS), polyisobutylene (PIB), and their oligomers. The results show that Cconfig could be well reproduced using the power and logarithmic functions based on the Landau theory that explains the vicinity of the critical point. The power and logarithmic functions had four and three fitting parameters, respectively. The error ranges were approximately ±2% for PS and ±5% for PIB.